Research and development of a semiconductor laser device for next generation DVDs is proceeding. Generally, a semiconductor laser, which emits 400 nm band wavelength laser, is used and InGaAlN semiconductors are used in the semiconductor laser device for next generation DVDs.
In a conventional InGaAlN semiconductor laser, a double hetero junction is provided on a substrate, and a ridge waveguide, which is formed in an upper clad, is provided.
Generally, in the conventional semiconductor laser device made of the InGaAlN semiconductor, a front edge (emission edge) and a rear edge are mirror surfaces made by cleavage. There are numerous surface states in the front edge and the rear edge, so a non-light emitting recombination occurs. Near the front edge and the rear edge, carrier concentration is decreased and light is absorbed. So heat is generated from the edges and COD (Catastrophic Optical Damage) may occur.